Assessment of bond state in lap-shear joints by guided wave transmission monitoring
Abstract:This paper deals with the propagation of ultrasonic guided waves in adhesively-bonded lap-shear joints. The topic is relevant to ultrasonic bond inspection in aerospace components. Specifically, the propagation of the lowest-order, antisymmetric a0 mode through the joint is examined. This mode can be easily generated and detected in the field due to the predominant out-of-plane displacements at the surface of the test-piece.
The a0 strength of transmission is studied for three different bond states in aluminium joints, namely a fully cured adhesive bond, a poorly cured adhesive bond, and a slip bond. Theoretical predictions based on the Global Matrix Method indicate that the dispersive behaviour of the guided waves in the multilayer overlap is highly dependent on bond state. Experimental tests of the joints are conducted by a hybrid, broadband laser/air-coupled ultrasonic setup in a through-transmission configuration. This system does not require any wet coupling and it can be moved flexibly across the test piece. The Gabor Wavelet transform is employed to extract energy transmission coefficients in the 100 kHz–1.4 MHz range for the three different bond states examined. A rationale for the selection of the a0 excitation frequencies highly sensitive to bond state will be given.
Document Type: Research Article
Affiliations: 1: Associate Professor at the department of Structural Engineering of the University of California, San Diego, USA, and the Director of the NDE & Structural Health Monitoring Laboratory 2: University of California, San Diego 3: Department of Structural Engineering at the University of California, San Diego
Publication date: March 1, 2004
- Official Journal of The British Institute of Non-Destructive Testing - includes original research and devlopment papers, technical and scientific reviews and case studies in the fields of NDT and CM.
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